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UPSC Prelims MCQ Ecology, Biodiversity & Climate Change

The UPSC Civil Services Preliminary Examination tests candidates on a broad range of topics. Ecology, Biodiversity and Climate Change (often abbreviated as ECBC) constitute a highyield section because they intersect with environment, agriculture, health, energy and international policy. The following page provides a concise yet comprehensive overview of the subject, key concepts, and representative multiplechoice questions (MCQs) that frequently appear in the exam.

1. Core Concepts to Master

Ecology

  • Levels of organization: individual, population, community, ecosystem, biome, biosphere.
  • Energy flow: primary production, net primary productivity (NPP), trophic levels, ecological efficiency (10%).
  • Biogeochemical cycles: carbon, nitrogen, phosphorus, sulfur cycles sources, sinks and human perturbations.
  • Population dynamics: exponential vs. logistic growth, carrying capacity (K), r and Kselected species, densitydependent & independent factors.
  • Ecological succession: primary vs. secondary succession, climax community, pioneer species.
  • Island biogeography: speciesarea relationship, equilibrium theory (MacArthur & Wilson).

Biodiversity

  • Components: genetic, species, ecosystem diversity.
  • Hotspots: definition, criteria (1,500 km with 0.5% of worlds species and >70% habitat loss) and major Indian hotspots (Western Ghats, Himalayas, IndoMyanmar).
  • Conservation strategies: insitu (protected areas, biosphere reserves, community reserves) and exsitu (seed banks, zoos, gene banks).
  • Legal framework: Wildlife Protection Act 1972, Biodiversity Act 2002, CITES, National Biodiversity Authority.
  • Key indices: Species richness, ShannonWiener index, Simpsons index, Endemicity Index.

Climate Change

  • Greenhouse gases (GHGs): CO, CH, NO, fluorinated gases sources and Global Warming Potential (GWP).
  • Radiative forcing: definition, major contributors.
  • IPCC assessment cycles: AR5 (2014) and AR6 (20212022) key messages.
  • Impacts: temperature rise, sealevel rise, extreme weather, glacier retreat, ocean acidification, biodiversity loss.
  • Adaptation & mitigation: REDD+, NDCs, National Action Plan on Climate Change (NAPCC), renewable energy targets.
  • International regimes: UNFCCC, Kyoto Protocol, Paris Agreement, Glasgow Climate Pact.

2. Frequently Asked MCQs with Explanations

Q1. Which of the following statements about the carbon cycle is correct?
  1. More than 90% of atmospheric CO is taken up by the ocean each year.
  2. Terrestrial photosynthesis accounts for about 30% of total carbon fixation globally.
  3. Rock weathering is a shortterm sink for atmospheric CO.
  4. Deforestation reduces the terrestrial carbon sink, increasing atmospheric CO.
Answer: D. Deforestation reduces the terrestrial carbon sink, leading to higher atmospheric CO. Options A and C are false; oceans absorb ~25% of anthropogenic CO annually, and rock weathering acts over geological time scales. Option B underestimates the contribution terrestrial photosynthesis fixes roughly 120GtCyr, about half of total fixation.
Q2. The Island Biogeography Theory predicts that a smaller island will have:
  1. Higher species richness than a larger island.
  2. Lower equilibrium species number but higher turnover rate.
  3. Same number of species as a larger island if distance from mainland is the same.
  4. Lower extinction rate than a larger island.
Answer: B. A smaller island supports fewer species at equilibrium and experiences higher extinction rates, resulting in higher turnover.
Q3. Which of the following Indian protected areas is NOT a UNESCO World Heritage Site?
  1. Keoladeo National Park
  2. Great Himalayan National Park
  3. Kaziranga National Park
  4. Sunderbans National Park
Answer: D. While the Sunderbans is a Ramsar site and a Tiger Reserve, it is not yet listed as a UNESCO World Heritage Site (the mangroves are under consideration).
Q4. According to the Paris Agreement, the term NDC stands for:
  1. National Development Council
  2. Netdecarbonisation Commitment
  3. Nationally Determined Contribution
  4. NewDecade Climate
Answer: C. NDC = Nationally Determined Contribution, the pledge each country makes to reduce GHG emissions.
Q5. Which of the following best describes Ecological Efficiency?
  1. The proportion of solar energy converted into chemical energy by a primary producer.
  2. The proportion of energy transferred from one trophic level to the next.
  3. The ratio of biomass produced to biomass consumed within a community.
  4. The percentage of carbon fixed by forests relative to global land carbon uptake.
Answer: B. Ecological efficiency 10% of energy passes from one trophic level to the next.

3. Quick Revision Tips

  • Make a formula sheet: NPP = GPP R; Logistic growth: dN/dt = rN(1N/K).
  • Use mnemonics: CANDU for carbon cycle reservoirs CO in Atmosphere, Oceans, Northland (soil), Deforestation (land use), Urban emissions.
  • Bookmark key numbers:
    • Global mean temperature rise since preindustrial: ~1.1C.
    • Sea level rise projected by 2100 (RCP8.5): 0.61.1m.
    • Indias renewable energy target 2030: 500GW.
  • Crosslink topics: Relate biodiversity loss to climate impacts (e.g., coral bleaching) and to policy instruments (e.g., REDD+).
  • Practice old papers: Identify recurring askthefact questions (e.g., Which of the following is a hotspot?) versus applicationoriented ones (e.g., What will be the likely impact of shifting monsoon onset on Himalayan ecosystems?).

4. Suggested Reading & Resources

  • NCERT Class XI & XII Biology & Geography (chapters on ecosystems, climate).
  • India: Biodiversity Hotspots Ministry of Environment & Forests (PDF).
  • IPCC Summary for Policymakers (latest AR6) concise bullet points.
  • World Bank Climate Change Knowledge Portal uptodate data on temperature trends.
  • Previous UPSC Question Papers focus on years 20152023 for trend analysis.

5. Mock Test 5 Question Set

Try solving these within 5 minutes. Check your answers against the explanations above.

  1. Which GHG has the highest global warming potential over a 100year horizon?
    A) COB) CHC) NOD) SF
  2. The Allee effect is associated with:
    A) Decrease in population growth at low densitiesB) Increase in genetic driftC) Higher predator efficiencyD) Greater ecosystem resilience
  3. Under the NAPCC, the focal area National Mission for Sustaining the Himalayan Ecosystem primarily addresses:
    A) Renewable energyB) Water securityC) Glacier meltD) Soil erosion
  4. Which of the following is NOT a criterion for identifying an Ecologically Sensitive Area (ESA) in India?
    A) Presence of endangered speciesB) High rainfall varianceC) Unique geological featuresD) Low human footprint
  5. Blue carbon refers to carbon stored in:
    A) Forest biomassB) Deepsea sedimentsC) Mangroves, seagrasses and tidal marshesD) Freshwater lakes

Use this page as a starter guide. Deepen each point with diagrams, flowcharts and countryspecific data for a robust preparation.

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